1. Field of the Invention
The present invention relates to a process cartridge, an assembling method for such a process cartridge, and an image forming system on which such a process cartridge can be mounted. Such an image forming system may be embodied, for example, as an electrophotographic copying machine, a laser beam printer, a facsimile, a word processor or the like.
2. Related Background Art
In image forming systems such as copying machines, a latent image is formed by selectively exposing a uniformly charged image bearing member, the latent image is then visualized with toner, and then the toner image is transferred onto a recording sheet, thereby forming an image on the recording sheet. In such image forming systems, whenever the toner is used up, it must replenished with new toner. The toner replenishing operation not only is troublesome, but also often causes contamination of the surroundings. Further, since the maintenance of various elements or members can be performed only by an expert in the art, most of the users are inconvenienced.
To eliminate such drawback and inconvenience, an image forming system, wherein parts such as a developing device, which toner therein is used up, or an image bearing member, which a service life thereof has expired, can easily be exchanged, thereby facilitating the maintenance, by assembling the image bearing member, a charger, the developing device and a cleaning device integrally as a process cartridge, which can be removably mounted within the image forming system, has been proposed and put into practical use, for example, as disclosed in U.S. Pat. Nos. 3,985,436, 4,500,195, 4,540,268 and 4,627,701.
Now, a construction of a conventional process cartridge will be explained. In the conventional process cartridge, a cleaning device and a developing device are arranged with the interposition of a photosensitive drum, and a toner container is disposed substantially above the developing device and is contacted therewith. Further, a charger device is disposed substantially above the photosensitive drum.
The cleaning device serves to remove the residual toner remaining on the photosensitive drum, thus preparing for the next image formation, and comprises a cleaning container for collecting the waste toner, a cleaning blade slidingly contacting with the photosensitive drum to remove or scrape the residual toner from the latter, a dip sheet for directing the removed waste toner to the cleaning container, and an agitating member for conveying the waste toner in the cleaning container toward the interior of the latter. The cleaning blade is fixedly attached to the cleaning container by screws or an adhesive.
On the other hand, the developing device serves to visualize an electrostatic latent image formed on the photosensitive drum by supplying the toner to the latent image, and comprises a developing container defining a developing chamber, and a developing blade for charging the toner while slidingly contacting a developing sleeve for supplying the toner, and for forming a toner layer having uniform thickness on the developing sleeve. The developing container has an opening formed in a surface thereof opposite to the photosensitive drum, and is connected to a toner container containing the toner in such a manner that the opening of the developing container is aligned with an opening formed in the toner container. The developing blade is fixedly attached to the developing container by screws.
However, in the above-mentioned process cartridge, when the blades are attached to the corresponding containers, since the attachment directions were opposed to each other, it was feared that the assembling ability was worsened. Further, in the above-mentioned process cartridge, a distance between the developing device and the cleaning device was smaller than an outer diameter of the photosensitive drum. As a result, since the photosensitive drum had to be incorporated into the process cartridge before the developing blade or the cleaning blade was attached to a frame of the process cartridge, it was difficult to measure or check the attachment position and the contacting pressure of the cleaning blade and/or the developing blade.
Further, if the cleaning blade and/or the developing blade are closely contacted with the photosensitive drum and/or the developing sleeve before the toner is adhered to the cleaning blade and/or the developing blade (initial condition), it is feared that the rotational torque is increased and/or the blade(s) is turned up. In order to prevent the torque increase and the blade turn-up, lubricant must be applied to the cleaning blade and/or the developing blade before they are attached to the frame of the process cartridge. Consequently, it is possible that the lubricant applied to the blade(s) drops off of the blade(s) during the assembling of the blade(s). After either one of the cleaning blade or the developing blade has been assembled, if the photosensitive drum is incorporated into the process cartridge, the photosensitive drum will be contacted with a supporting member for the cleaning blade or a supporting member for the developing blade, thus damaging the surface of the photosensitive drum, which results in the poor image quality.
Incidentally, the techniques for assembling an image bearing member into a process cartridge are disclosed in U.S. Pat. Nos. 4,575,221, 4,708,455 and 4,888,620 and the like. The U.S. Pat. No. 4,575,221 discloses a technique where a developing device and a cleaning device are constituted as a unit and the unit is assembled into a frame of a process cartridge. The U.S. Pat. No. 4,708,455 discloses a technique that a developing unit, a cleaning unit and an image bearing member are removably assembled into a frame of a process cartridge. Further, the U.S. Pat. No. 4,888,620 discloses a technique where a process cartridge is mounted with respect to an image bearing member attached to an image forming system.